Multi-layer packaged article

ABSTRACT

The present invention provides a multi-layer packaged article that is excellent in pinhole resistance and transparency. Specifically, the present invention provides a multi-layer packaged article wherein a material is packaged with a multi-layer film having a layer comprising an ethylene-vinyl alcohol copolymer and the film is irradiated by ionizing radiation of 1 to 50 kGy at 10° C. or lower. In preferable embodiments of the present invention, the multi-layer film has a layer structure comprising a layer of linear low density polyethylene placed directly or via an adhesive layer on both faces of the layer containing EVOH and is subjected to ionizing radiation under an atmosphere of −40 to 5° C. Also, the ionizing radiation is preferably γ rays.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a multi-layer packaged articlewherein a material is packaged with a multi-layer film having a layercomprising an ethylene-vinyl alcohol copolymer (hereinafter referred toas EVOH). More preferably, the present invention relates to amulti-layer packaged article wherein food for chilled and frozenstorage, particularly livestock meat, is packaged by packaging materialthat is excellent in pinhole resistance and transparency.

[0002] Usually, EVOH is excellent in transparency, gas barrierproperties, aroma retaining properties, solvent resistance and oilresistance. Utilizing these properties, EVOH is used for variouspackaging materials such as packaging material for food, pharmaceuticalproducts, industrial chemicals and agricultural chemicals. Particularly,EVOH is widely used as food packaging, to package food such as livestockmeat, utilizing the properties of transparency and gas barrierproperties.

[0003] However, EVOH is inferior in pinhole resistance compared tothermoplastic resin such as polyolefin resin and polystyrene resin.

[0004] That is, when the packaged material is shaken, for example whiletransporting or carrying, the EVOH layer suffers bending fatigue andpinholes develop. As a result, barrier properties decrease.

[0005] As measures to solve the above problems, suggested are the methodof mixing EVOH and polyester resin (for example see JP-A-63-218352), themethod of mixing EVOH, polyolefin and a specific grafted substance (forexample see JP-A-3-227345), the method of mixing EVOH, nylon and anionomer (for example see JP-A-2000-246843) and the method of mixing EVOHand nylon having a low melting point (for example see JP-A-2002-338770).

[0006] As a result of detailed studies regarding the above compositions,the compositions described in JP-A-63-218352 and JP-A-3-227345 werefound to be improved in pinhole resistance. However, becausecompatibility of EVOH with the other resins is unfavorable and thecomposition takes on a sea-island structure when drawing treatment isconducted to impart shrinking property, which is necessary when usingfor meat packaging, gas barrier properties were found to decrease andtransparency was found to decrease, as the film became white.

[0007] The compositions described in JP-A-2000-246843 and JP-2002-338770were also found to have room for further improvement in pinholeresistance and film transparency, as compatibility of EVOH with nylonresin is too high.

[0008] Furthermore, in all of the above cases, pinhole resistance wasfound to decrease even further when exposed to a low temperatureatmosphere such as repeated transportation in a frozen state (forexample approximately −20° C.), as in the case of meat packaging.

SUMMARY OF THE INVENTION

[0009] As a result of intensive studies in light of the above, amulti-layer packaged article, wherein a material is packaged with amulti-layer film having a layer comprising an ethylene-vinyl alcoholcopolymer and the film is irradiated by ionizing radiation of 1 to 50kGy at 10° C. or lower, was found to solve the above problems. Thus, thepresent invention was achieved.

[0010] Furthermore, in preferable embodiments of the present invention,the multi-layer film has a layer structure comprising a layer of linearlow density polyethylene placed directly or via an adhesive layer onboth faces of the layer comprising EVOH and is subjected to ionizingradiation under an atmosphere of −40 to 5° C. Also, the ionizingradiation is preferably γ rays.

DETAILED DESCRIPTION

[0011] The present invention is described in detail below.

[0012] The EVOH used in the present invention is not particularlylimited. However, the ethylene content of EVOH is preferably 10 to 70%by mol, more preferably 20 to 60% by mol, further preferably 25 to 50%by mol, and the hydrolysis degree of the vinyl acetate component in EVOHis preferably at least 90% by mol, more preferably at least 95% by mol,further preferably at least 99% by mol. When the ethylene content isless than 10% by mol, gas barrier properties under high humidity andmelt moldability decrease. On the other hand, when the ethylene contentis more than 70% by mol, sufficient gas barrier properties are notobtained. When the hydrolysis degree of the vinyl acetate component isless than 90% by mol, gas barrier properties, thermal stability andhumidity resistance decrease, thus being unfavorable.

[0013] The melt flow rate (MFR) of EVOH (measured at 210° C. under loadof 2160 g, hereinafter the same) is not particularly limited, but ispreferably 0.5 to 100 g/10 minutes, more preferably 1 to 50 g/10minutes, particularly preferably 3 to 35 g/10 minutes. When the meltflow rate is lower than the above range, the inside of the extruder whenmolding is under high torque conditions and extrusion processing tendsto become difficult. When the melt flow rate is higher than the aboverange, moldability decreases and the thickness precision of the layercontaining EVOH in the obtained multi-layer film decreases, thus beingunfavorable.

[0014] The EVOH is obtained by hydrolysis of an ethylene-vinyl acetatecopolymer. The ethylene-vinyl acetate copolymer is prepared by any knownpolymerization method such as solution polymerization, suspensionpolymerization and emulsion polymerization and hydrolysis of theethylene-vinyl acetate copolymer can be conducted by a known method.

[0015] In the present invention, a copolymerizable ethylenic unsaturatedmonomer can be copolymerized as long as the effects of the presentinvention are not inhibited. Examples of the monomer are olefins such aspropylene, 1-butene and isobutene; unsaturated acids such as acrylicacid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid,(anhydrous) maleic acid and (anhydrous) itaconic acid, salts thereof ormono or dialkylesters thereof having 1 to 18 carbon atoms; acrylamidessuch as acrylamide, N-alkylacrylamide having 1 to 18 carbon atoms,N,N-dimethylacrylamide, 2-acrylamidepropane sulfonic acid, salt thereof,acrylamide propyldimethylamine, acid salt thereof and quaternary saltthereof, methacrylamides such as methacrylamide, N-alkylmethacrylamidehaving 1 to 18 carbon atoms, N,N-dimethylmethacrylamide,2-methacrylamidepropane sulfonic acid, salt thereof, methacrylamidepropyldimethylamine, acid salt thereof and quaternary salt thereof;N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide andN-vinylacetoamide; cyanized vinyls such as acrylonitrile andmethacrylonitrile; vinyl ethers such as alkylvinylether having 1 to 18carbon atoms, hydroxyalkylvinylether and alkoxyalkylvinylether;halogenated vinyls such as vinyl chloride, vinylidene chloride, vinylfluoride, vinylidene fluoride and vinyl bromide; vinyl silanes such astrimethoxyvinyl silane; allyl acetate; allyl chloride; allyl alcohol;dimethylallyl alcohol;trimethyl-(3-acrylamide-3-dimethylpropyl)-ammonium chloride andacrylamide-2-methylpropane sulfonic acid. The above monomers can bepost-modified, for example, urethanized, acetalized or cyanoethylized,as long as the effects of the present invention are not lost.

[0016] As the EVOH, at least two different kinds of EVOH can be used. Insuch a case, by using a mixture of EVOH wherein the ethylene contents ofthe compounded EVOH differ at least 5% by mol, preferably 5 to 25% bymol, more preferably 8 to 20% by mol, and/or the hydrolysis degreesdiffer at least 1% by mol, preferably 1 to 15% by mol, more preferably 2to 10% by mol, and/or the ratio of MFR is at least 2, preferably 3 to20, more preferably 4 to 15, flexibility, thermal moldability andfilm-forming stability are improved, while maintaining gas barrierproperties. The process for preparing the EVOH (mixture) of at least twodifferent kinds is not particularly limited. Examples are the method ofmixing the paste of each ethylene-vinyl acetate copolymer beforehydrolysis and then hydrolyzing, the method of mixing the alcohol oralcohol and water solution of each EVOH after hydrolysis and the methodof melt kneading after mixing each EVOH.

[0017] The EVOH used in the present invention can contain acids such asacetic acid, boric acid and phosphoric acid and metal salts thereof suchas alkali metal salt, alkali earth metal salt and transition metal salt.The above are preferably contained from the viewpoints that thermalstability of EVOH, long-run moldability, interlayer adhesion to theadhesive resin when made into a multi-layer film using an adhesive andthermal drawing moldability are improved. Particularly, alkali metalsalt and alkali earth metal salt are preferably used, from the viewpointof being excellent regarding the above effects.

[0018] Examples of the metal salt are metal salt such as sodium salt,potassium salt, calcium salt and magnesium salt of organic acidsincluding acetic acid, propionic acid, butyric acid, lauric acid,stearic acid, oleic acid and behenic acid and inorganic acids includingsulfuric acid, sulfurous acid, carbonic acid and phosphorous acid. Ofthese, acetate, phosphate and hydrogen phosphate are preferably used.The content of the metal salt is preferably 5 to 1000 ppm, morepreferably 10 to 500 ppm, further preferably 20 to 300 ppm, converted tometal based on the EVOH. When the content is less than 5 ppm, theeffects of adding may be insufficient and on the other hand, when thecontent is more than 1000 ppm, the appearance of the obtainedmulti-layer film becomes poor, thus being unfavorable. In the case thattwo or more kinds of alkali metal salt and/or alkali earth metal saltare contained, the total amount is preferably within the above range.Also, when boric acid is contained, the content is preferably 10 to10000 ppm, more preferably 20 to 2000 ppm, further preferably 50 to 1000ppm converted to boric acid.

[0019] The method for adding the acids or metal salts thereof to theEVOH is not particularly limited. Examples are a) the method ofcontacting porous precipitate of EVOH having water content of 20 to 80%by weight with an aqueous solution of the acid or metal salt thereof andthen drying after the EVOH has contained the acid or salt thereof; b)the method of adding the acid or metal salt thereof to a homogenoussolution of EVOH (such as water/alcohol solution), extruding in strandsinto a coagulation solution, cutting the obtained strands to formpellets and then drying; c) the method of mixing EVOH and the acid orsalt thereof all at once and then melt kneading in an extruder; and d)the method of neutralizing the alkali (such as sodium hydroxide,potassium hydroxide) used in the hydrolysis step when preparing EVOHwith an acid such as acetic acid and then adjusting the amount of theremaining acid such as acetic acid and alkali metal salt such as sodiumacetate and potassium acetate that is by-produced by washing with water.In order to achieve the effects of the present invention morenoticeably, the methods a), b) and d), which are excellent indispersability of the acid or metal salt thereof, are preferably used.

[0020] In the present invention, as long as the effects of the presentinvention are not lost, the layer comprising EVOH can contain saturatedfatty acid amides such as stearamide; unsaturated fatty acid amides suchas oleamide; bis fatty acid amides such as ethylenebis(stearamide);fatty acid metal salt such as calcium stearate, magnesium stearate andzinc stearate; lubricants such as low molecular weight polyolefinincluding low molecular weight polyethylene and low molecular weightpolypropylene having molecular weight of approximately 500 to 10,000;inorganic salt such as hydrotalcite; plasticizers such as aliphaticpolyol including ethylene glycol, glycerin and hexanediol; oxygenabsorbents such as inorganic oxygen absorbents including reduced ironpowder, reduced iron powder to which water-absorbing substances orelectrolyte is added, aluminum powder, potassium sulfite andphotocatalytic titanium oxide, organic oxygen absorbents includingascorbic acid, fatty esters and metal salts thereof, hydroquinone,gallic acid, polyphenols including phenol-aldehyde resin having ahydroxyl group, coordination compounds of nitrogen-containing compoundsand transition metal including bis-salicylaldehyde-iminecobalt,tetraethylenepentaminecobalt, cobalt-Schiff base complex, porphyrins,macrocyclic polyamine complex and polyethyleneimine-cobalt complex,terpene compounds, reaction products of amino acids and reducingsubstances having a hydroxyl group, and triphenylmethyl compounds, andpolymer oxygen absorbents such as coordinate bonded bodies ofnitrogen-containing resin and transition metal including a combinationof metaxylenediamine and cobalt, compositions of tertiaryhydrogen-containing resin and transition metal including a combinationof propylene oligomer and cobalt, compositions of oligomer having acarbon-carbon unsaturated bond and transition metal including acombination of butadiene oligomer and cobalt, anthraquinone compounds,and the above compositions to which a photoinitiator such asbenzophenone, a peroxide collecting agent such as commercially availableantioxidants and a deodorant such as active carbon is added; thermalstabilizers; photostabilizers; antioxidants; ultraviolet ray absorbents;colorants; antistatic agents; surfactants; antibacterial agents;antiblocking agents such as fine powder of talc; slipping agents such asamorphous silica; and fillers such as inorganic fillers.

[0021] The EVOH is preferably used in a laminate, particularly in alaminate wherein a thermoplastic resin layer is laminated on at leastone face of the layer comprising EVOH. The obtained laminate has waterresistance, mechanical properties and heat sealing properties and issuitable for practical use.

[0022] The multi-layer film used in the multi-layer packaged article ofthe present invention is a multi-layer film having a layer containingEVOH (hereinafter referred to as EVOH layer). To obtain the multi-layerfilm, usually, another substrate such as thermoplastic resin islaminated on one face or both faces, preferably both faces, of the EVOHlayer.

[0023] Examples of the laminating method are the method of laminating bymelt extruding the other substrate on the EVOH layer (film or sheet),the method of laminating by melt extruding the EVOH on the othersubstrate, the method of co-extruding the EVOH and the other substrateand the method of dry laminating the EVOH layer and a film or sheet ofthe other substrate using a known adhesive such as an organic titaniumcompound, an isocyanate compound, a polyester compound and apolyurethane compound. The melt molding temperature when laminating bymelt extrusion or co-extrusion is usually within the range of 150 to300° C.

[0024] As the other substrate, thermoplastic resin is useful.Specifically, examples are linear low density polyethylene; low densitypolyethylene; ultra low density polyethylene; medium densitypolyethylene; high density polyethylene; ethylene-vinyl acetatecopolymer; ionomer; ethylene-propylene (block or random) copolymer;ethylene-acrylic acid copolymer; ethylene-acrylic ester copolymer;polypropylene; propylene-α-olefin (α-olefin having 4 to 20 carbon atoms)copolymer; polyolefin resin in a broad sense such as homopolymer orcopolymer of olefin including polybutene and polypentene and homopolymeror copolymer of these olefins that is graft-modified with unsaturatedcarboxylic acid or ester thereof; polyester resin, polyamide resin(including copolymerized polyamide); polyvinyl chloride; polyvinylidenechloride; acrylic resin; polystyrene; vinyl ester resin; polyesterelastomer; polyurethane elastomer; chlorinated polyethylene; chlorinatedpolypropylene; aromatic or aliphatic polyketone; polyalcohols obtainedby reducing these; and other EVOH. From the viewpoint of practicabilitysuch as properties, particularly strength, of the multi-layer film,polypropylene, ethylene-propylene (block or random) copolymer,polyamide, polyethylene, ethylene-vinyl acetate copolymer, polystyrene,polyethylene terephthalate and polyethylene naphthalate are preferablyused. Of these, linear low molecular weight polyethylene is particularlypreferable.

[0025] When the EVOH layer is represented as a (a₁, a₂ . . . ) and theother substrate such as the thermoplastic resin layer is represented asb (b₁, b₂ . . . ), the layer structure of the multi-layer film is notlimited to the two-layer structure of a/b and any combination ispossible, such as b/a/b, a/b/a, a₁/a₂/b, a/b₁/b₂, b₂/b₁/a/b₁/b₂ andb₂/b₁/a/b₁/a/b₁/b₂. Furthermore, when a regrind layer comprising amixture of at least EVOH and thermoplastic resin is represented as R,the layer structure can be b/R/a, b/R/a/b, b/R/a/R/b, b/a/R/a/b orb/R/a/R/a/R/b.

[0026] In the above layer structure, a layer of adhesive resin ispreferably formed when necessary between each layer, from the viewpointthat a multi-layer film that is excellent in drawing properties can beobtained. Various resins can be used as the adhesive resin and althoughthe preferable type of adhesive resin depends on the type of resin b,examples are modified olefin polymers containing a carboxyl group thatare obtained by chemically bonding unsaturated carboxyl acid oranhydride thereof to an olefin polymer (polyolefin resin in a broadsense described above) by addition reaction or graft reaction.Specifically, suitable examples are one or at least two compositionsselected from polyethylene graft-modified with maleic anhydride,polypropylene graft-modified with maleic anhydride, ethylene-propylene(block or random) copolymer graft-modified with maleic anhydride,ethylene-ethyl acrylate copolymer graft-modified with maleic anhydrideand ethylene-vinyl acetate copolymer graft-modified with maleicanhydride. The amount of unsaturated carboxylic acid or anhydridethereof that is contained in the thermoplastic resin is preferably 0.001to 3% by weight, more preferably 0.01 to 1% by weight, furtherpreferably 0.03 to 0.5% by weight. When the modified amount in themodified substance is small, adhesion may be insufficient and when theamount is large, crosslinking reaction occurs and moldability tends tobecome poor, thus being unfavorable. To the adhesive resin, EVOH,polyisobutylene, rubber elastomer components such as ethylene-propylenerubber and resin of layer b can be mixed. Particularly, mixing apolyolefin resin that is different from the matrix polyolefin resin ofthe adhesive resin is useful, as adhesion may be improved.

[0027] The thickness of each layer of the multi-layer film depends onthe layer structure, the type of resin b, the type and shape of thelivestock meat that is to be packaged, the form of packaging (container)and the desired properties. Usually, the thickness of layer a is 5 to500 μm, preferably 10 to 200 μm, the thickness of layer b is 10 to 5000μm, preferably 30 to 1000 μm, and the thickness of the adhesive resinlayer is 5 to 400 μm, preferably 10 to 150 μm.

[0028] When layer a is thinner than 5 μm, gas barrier properties areinsufficient and also, the thickness cannot be controlled withstability. On the other hand, when the thickness is more than 500 μm,drawing properties and pinhole resistance tend to decrease andeconomical efficiency decreases, thus being unfavorable. When layer b isthinner than 10 μm, rigidity is insufficient and when the thickness ismore than 5000 μm, the weight becomes large and economical efficiencydecreases, thus being unfavorable. When the adhesive resin layer isthinner than 5 μm, interlayer adhesion is insufficient and also, thethickness cannot be controlled with stability. On the other hand, whenthe thickness is more than 400 μm, the weight becomes large andeconomical efficiency decreases, thus being unfavorable.

[0029] The material that is packaged by the multi-layer film obtained inthe above manner is not particularly limited. Examples are livestockmeat such as beef, pork, poultry and mutton; processed meat productssuch as ham, sausage, salami, roast pork and roast chicken; fish pasteproducts such as kamaboko (fish cake) and delicacies and processedagricultural products such as rice cakes, pickles, cheese and mountainvegetables. The present invention is useful as packaging for livestockmeat. Use of the present invention as packaging for livestock meat isdescribed below but the present invention is not limited thereto.

[0030] When packaging livestock meat, the multi-layer film can be usedas it is, but usually, the multi-layer film is subjected to drawingtreatment in order to impart thermal contraction properties and becomeshrink packaging. Examples of the drawing method are the roll drawingmethod, the tenter drawing method, the tubular drawing method, the drawblowing method, vacuum molding, pneumatic molding and vacuum pneumaticmolding and of these, a method having high drawing ratio is employed. Inthe case of biaxial drawing, both simultaneous biaxial drawing andsequential biaxial drawing can be employed. The drawing temperature is60 to 170° C., preferably 80 to 160° C.

[0031] The film subjected to drawing treatment is then processed into apouch. The shape of the pouch can be determined according to the shapeof the contents. After livestock meat is stored in the pouch, thermaltreatment is conducted at 50 to 130° C., preferably 70 to 120° C., forabout 2 to 300 seconds to thermally contract the film and obtain atightly packaged article.

[0032] The livestock meat stored in the packaging pouch can be meat forhuman consumption that is bred as livestock and specific examples arebeef, pork, poultry and mutton. The livestock meat can be unprocesseddressed carcass having bones or processed boneless meat dividedaccording to each part.

[0033] The present invention is most characteristic in that themulti-layer EVOH film that constitutes the multi-layer packaged articleis irradiated by ionizing radiation of 1 to 50 kGy at 10° C. or lower.The livestock meat can be packaged with the multi-layer EVOH film beforeirradiation or after irradiation, but in view of production efficiency,the former is preferable.

[0034] Irradiation treatment is described below.

[0035] The temperature when irradiating is at most 10° C., preferably−60 to 10° C., more preferably −40 to 5° C., further preferably −25 to−5° C. When the temperature is higher than 10° C., pinhole resistancedecreases and achieving the purpose of the present invention may bedifficult. The temperature can be adjusted to this range byrefrigerating or by freezing.

[0036] The amount of ionizing radiation is 1 to 50 kGy, preferably 5 to40 kGy, more preferably 15 to 30 kGy. When the amount is less than 1kGy, the effects of the present invention may not be obtained. On theother hand, when the amount is more than 50 kGy, foul odor is generateddue to decomposition of resin in the multi-layer film, thus beingunsuitable.

[0037] Examples of the ionizing radiation are α-rays, β-rays, γ-rays,electron rays and neutron rays. From the viewpoint of ease in handling,γ-rays and electron rays are preferably used and γ-rays is morepreferably used from the viewpoint that even irradiation is possible.

[0038] The type of γ-rays is not particularly limited and γ-rays emittedfrom a radiation source such as cobalt 60 and cesium 137 are preferablyused.

[0039] In this way, the multi-layer packaged article of the presentinvention, which is excellent in pinhole resistance and transparency, isobtained.

[0040] Hereinafter, the present invention is described in detail basedon Examples.

[0041] In Examples, “parts” and “%” represent weight standards unlessindicated otherwise.

EXAMPLE1

[0042] <Preparation of Multi-layer Film>

[0043] EVOH (ethylene content 32% by mol, hydrolysis degree 99.5% bymol, MFR 3.5 g/10 minutes), polyethylene (linear low densitypolyethylene, “Novatech LLUF 331” available from Japan PolychemCorporation, MFR 1.0 g/10 minutes) and adhesive resin (low densitypolyethylene modified with maleic anhydride, “MODIC AP L502” availablefrom Mitsubishi Chemical Corporation) were fed to a multi-layerextruding apparatus equipped with 3 kinds of feed blocks and amulti-layer T die of five layers. Then, a multi-layer film having alayer structure of polyethylene layer/adhesive resin layer/EVOHlayer/adhesive resin layer/polyethylene layer (thickness 40/10/30/10/40μm) was obtained.

[0044] <Packaging of Livestock Meat>

[0045] The multi-layer film obtained above was subjected to simultaneousbiaxial drawing at a temperature of 75° C. and a drawing rate of 50mm/sec to three times in the TD direction and three times in the MDdirection, to obtain a drawn multi-layer film. Then, using two of theabove drawn multi-layer films, a pouch sealed in three directions havingwidth of 200 mm, length of 300 mm and sealing width of 15 mm wasprepared. Approximately 1 kg of dressed Boston butt (cube having lengthof 15 cm, width of 10 cm and height of 6 cm) was placed in the pouch andthe upper area was vacuum sealed by a vacuum packaging machine.Thereafter, the packaged pouch was thermally contracted by a hot watershower of 80° C. for 4 seconds and then cooled in water of 5° C. for 3minutes to obtain a multi-layer packaged article of livestock meat.

[0046] <Ionizing Radiation Treatment>

[0047] The obtained packaged article was frozen at −20° C. and 24 hourslater, EB irradiation of acceleration voltage of 200 MeV and amount of25 kGy was conducted in an environment of −20° C. to obtain themulti-layer packaged article of the present invention.

[0048] The multi-layer packaged article obtained above was evaluated inthe following manner.

[0049] (Pinhole Resistance)

[0050] One set comprising 12 of the above multi-layer packaged articleswas placed in a cardboard box in two levels with 3 pouches in the lengthdirection and 2 pouches in the width direction. The box was stowed inthe loading space of a refrigerated 2 ton truck (inside temperature −20°C.) and the truck made two round trips in one week between Yokohama andKobe. Thereafter, the content of the two packages in the middle of thebottom level was taken out and the oxygen permeation degree of the film(average value of n=2) was measured under conditions of 23° C. and 80%RH.

[0051] (Transparency)

[0052] The haze value of the film after the above pinhole resistancetest (thickness of approximately 100 μm) was measured using “Haze MeterNDH 2000” made by Nippon Denshoku Industries Co., Ltd.

EXAMPLE 2

[0053] The multi-layer packaged article was obtained and evaluated inthe same manner as in Example 1, except that 25 kGy of γ-rays emittedfrom cobalt 60 as the radiation source were irradiated as the ionizingradiation.

EXAMPLE 3

[0054] The multi-layer packaged article was obtained and evaluated inthe same manner as in Example 2, except that the packaged article wasirradiated at an irradiation temperature of 5° C. by 25 kGy of γ-raysemitted from cobalt 60 as the radiation source and then frozen at −20°C.

COMPARATIVE EXAMPLE 1

[0055] The multi-layer packaged article was obtained and evaluated inthe same manner as in Example 1, except that ionizing radiation was notirradiated.

COMPARATIVE EXAMPLE 2

[0056] The multi-layer packaged article was obtained and evaluated inthe same manner as in Example 1, except that the packaged article wasirradiated at an irradiation temperature of 20° C. and then frozen at−20° C.

[0057] The evaluation results of Examples and Comparative Examples areshown in Table 1. TABLE 1 Transparency Pinhole resistance (Haze value)Ex. 1 1.8 4.2 Ex. 2 1.6 3.8 Ex. 3 2.5 4.0 Com. Ex. 1 7.0 5.5 Com. Ex. 26.5 4.5

[0058] The multi-layer packaged article of the present invention hasexcellent pinhole resistance and transparency, because the article ispackaged with a multi-layer film having a layer comprising EVOH andirradiated by ionizing radiation of 1 to 50 kGy at a temperature of 5°C. or lower. Particularly, the multi-layer packaged article of thepresent invention is useful as a multi-layer packaged article oflivestock meat for human consumption such as beef, pork, poultry andmutton.

What is claimed is:
 1. A multi-layer packaged article wherein a materialis packaged with a multi-layer film having a layer comprising anethylene-vinyl alcohol copolymer; and said film is irradiated byionizing radiation of 1 to 50 kGy at 10° C. or lower.
 2. The multi-layerpackaged article of claim 1, wherein said film has a layer structurecomprising a layer of linear low density polyethylene placed directly orvia an adhesive layer on both faces of said layer comprising anethylene-vinyl alcohol copolymer.
 3. The multi-layer packaged article ofclaim 1, wherein said film is subjected to ionizing radiation in anatmosphere of −40 to 5° C.
 4. The multi-layer packaged article of claim1, wherein said ionizing radiation is γ rays.
 5. The multi-layerpackaged article of claim 1, wherein said material is livestock meat.